1. Field of the Invention
The invention generally relates to bicycle or velocipede training equipment. More specifically, this invention relates to a bicycle crank set with removable crank arms and pedals for training purposes that does not alter the sprocket or chain assembly.
2. Related Art
Scottish blacksmith Kirkpatrick Macmillan produced a crude version of today""s modem bicycle by in the mid 19th century. This bicycle had a steering mechanism and a cranking mechanism comprising pedals connected by a rod within the rear wheel. Over the years, various improvements have added to Macmillan""s crank design including:
Scott (U.S. Pat. No. 627,597) revealed a MEANS FOR ATTACHING SPROCKET WHEELS TO CRANK-SHAFTS in 1898. The design interlocks a sprocket with a single-piece bicycle crankshaft for use of a chain drive mechanism.
Osborne (U.S. Pat. No. 846,239) discusses a CRANK HANGER with inwardly hanging shaft-sections wherein one shaft-has a tapered end and another has a tapered recess to receive the tapered end. One crank arm has threads for screwing on the sprocket.
Thun (U.S. Pat. No. 3,906,811) VELOCIPEDE TREAD CRANK and Thun (U.S. Pat. No. 4,171,822) DUAL PEDAL CRANK ASSEMBLY FOR BICYCLES both depict two-piece bicycle crank arms that thread upon each other on the side of the bicycle extending away from the sprocket.
The LIGHT-WEIGHT BICYCLE CRANKSHAFT ASSEMBLY UTILIZING TWO-PIECE AXLE INTEGRALLY JOINED TO CRANK ARMS proposed by Edwards (U.S. Pat. No. 5,493,937) comprises two integrally attached hollow crank arms one with a male head member and another with a female receptacle. Schlangei (U.S. Pat. No. 5,941,135) is also a BICYCLE CRANKSHAFT ASSEMBLY that also connects two portions of a crank axle to one another in a similar fashion.
Richardson (U.S. Pat. No. 5,924,336) describes a HOLLOW BICYCLE CRANKSHAFT where one axle shaft member matingly engages a second axle shaft member and housed within a tubular housing member that secures the assembly in a coaxial and concentric alignment.
These improvements benefit riding efficiency. On the other hand, tools for learning how to ride a bike have seen few improvements:
Training wheels are the staple learning tool of youngsters and adults. While useful, many young children do not have the strength to operate a bicycle using the pedals and require pedal removal to propel the bicycle under foot power. This removal helps prevent the child""s shins from striking the pedal mechanism, but still leaves the crank arms in place, which can strike the child""s shins or cause the child to get xe2x80x9ctangled upxe2x80x9d in the crank arms and fall.
Stringer (U.S. Pat. No. 5,315,896) portrays a QUICK RELEASE BICYCLE PEDAL that addresses this method with a push button mechanism along the pedal""s lateral axis at the outermost portion from the bicycle frame itself. Similarly, Lin (U.S. Pat. 5,586,472) displays a DETACHABLE BICYCLE PEDAL MOUNTING STRUCTURE with a quick release mechanism along the longitudinal axis located at the area where the pedal connects with the crank arm.
Conventional systems for training children to ride bicycles have not fully addressed injuries that individuals sustain while learning to ride a bicycle using non-pedal foot power. For example, Stringer and Lin remove pedals. Yet, the crank arms remain on the bicycle and may still impact the learner""s shins and increase chances of a fall.
Still, there is a need for a device that overcomes many of the deficiencies of the prior art by providing a strong crank assembly that can be removed while leaving the bicycle chain and sprocket in place. There is a need for crank arms and pedals that are easily-removed without having to remove or move the hub assembly or chain assembly. There is a need for such a device that is economical and durable.
The invention comprises a system for convenient removal of pedals and crank arms from a bicycle for operation of the bicycle by foot-power, for example. The invented system provides a sturdy and stable crank set for normal bicycle operation, which crank set may be removed with a common tool(s) when the crank arms and/or pedals will be in a person""s way. Preferably, the invented system comprises a shaft-within-a-shaft system, including an internal shaft that is easily removable from the bicycle and that takes with it the crank arms. The shaft-within-a shaft system preferably includes: 1) an external shaft that is rotatably contained in the hub assembly in contact with the bearings and fixedly connected to the sprocket, and 2) a removable internal shaft that is connected to the crank arms, and which, when installed for use, is inside, generally coaxial with, and frictionally fixed to, the external shaft.
The preferred external shaft is disposed within the bearing retainer cups of a bicycle frame bottom hub assembly, and cooperates with a sprocket or spider assembly. The external shaft is fixedly connected to the sprocket/spider assembly preferably at one of its ends.
The internal shaft-crank arm combination is installed through the external shaft in such a way that preferably tightens the internal shaft tightly inside the external shaft by frictional engagement. Preferably, this is done by the internal shaft being in two parts, which each hold a crank arm and which each enter the external shaft from opposite ends. The two parts are connected preferably by a fastener, such as a bolt, screw, or other preferably-single fastener that secures the two internal shaft portions together inside the external shaft, generally at a midpoint along the combined internal shaft. Preferably, the internal shaft two portions are inserted into the external shaft from opposite ends of the shaft and connect together near the middle of the external shaft so that the resulting, installed combination is sturdy and reliable. The preferred single bole both fixes the two internal shaft parts to each other and causes the internal shaft to tighten its frictional engagement with the inside surface of the external shaft. For removal of the internal shaft and crank arms, the bolt may be removed from the internal shaft, which loosens the internal shaft relative to the external shaft and allows the two parts of the internal shaft to come apart and be pulled out from opposite ends of the external shaft. Thus, the internal shaft and its crank arms and pedals are removed, while leaving the external shaft and sprocket assembly intact.